Rifle Cartridge

ABSTRACT

A rifle cartridge is formed to have an overall length of about 2.800 inches, or 71.12 millimeters. The shell case has a case length between 1.900 inches and 1.950 inches and a neck forming a mouth for a standard .270 caliber bullet. The shoulder adjoining the neck widens from the neck to a diameter of between 0.445 inches to 0.465 inches, and preferably 0.450 inches. The adjoining shell body forms the main powder chamber for receiving an explosive charge. A head adjoins the shell body and forms a base of the shell case. The head has a primer pocket formed therein communicating with the main powder chamber through a vent hole formed between the primer pocket and the main powder chamber.

BACKGROUND OF THE INVENTION Field of the Invention

The invention lies in the field of interior ballistics and relates, morespecifically, to a novel cartridge. Ballistics is generally divided intothree distinct categories, namely, interior ballistics, exteriorballistics, and terminal ballistics. Here we deal exclusively withinterior ballistics.

A variety of parameters influence the ballistic behavior ofpowder-accelerated ammunition. In terms of the interior ballistics, theshape of the and dimensions of the cartridge shell (relative to theinterior bore dimensions of the gun chamber), the amount andcharacteristics of the propellant (powder) charge, the primer and theprimer vent connection to the main cartridge chamber are some of theprimary aspects of interior ballistics behavior. Pressure and head spaceparameters are also important and they must be balanced against theother parameters.

This invention relates to rimmed cartridges and to rimless cartridges.Rimmed cartridges are provided with a base that has a wider diameterthan the main body of the cartridge. The wider base forms a rim aroundthe cartridge bottom with which the cartridge rests against the entryrim of the chamber. The base of rimless cartridges typically has thesame or even smaller diameter than the body. The cartridge sits in andbraces against the chamber walls to define its insertion depth. Anextraction groove remains outside the chamber so as to allow thecartridge shell to be removed after the bullet has been fired.

In the following description the novel cartridge (the “0.270 Schuster”)will be compared primarily with the 0.308 Winchester (i.e., the 7.62×51mm NATO centerfire cartridge) and with the 0.270 Winchester. The formeris probably one of the most popular and successful hunting, competition,and sharp-shooting cartridges.

The 0.308 Winchester was adopted with a standard 146 grain bullet.Loading manuals present data for bullet weights up to 200 grains.Bullets weights of 168 provide for very impressive performance inserious target competition. Further, generally heavy weighted bulletsare a good choice for shooting longer distances. Bullet weights from 174to 190 grains are especially popular for long range shooting.

These bullet weights, however, result in considerable recoil, which isunacceptable to many shooters. Mid-range weights from about 145 to 155grain deliver acceptable recoil performance for most shooters. The 0.308Winchester cartridge is overpowered for many shooting applications andthe recoil presents a problem with regard to gun control in time-limitedshooting disciplines.

BRIEF SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a riflecartridge, which overcomes the above-mentioned disadvantages of theheretofore-known devices of this general type and which provides for anew cartridge with a lower energy potential but with similar or evenbetter features and ballistics for the preferred bullet weights atapproximately 145 to 155 grain.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a rifle cartridge, comprising:

-   -   a shell case having a case length between 1.900 inches and 1.950        inches and having a neck forming a mouth for a standard .270        caliber bullet;    -   a shoulder adjoining said neck and widening from said neck to a        diameter of between 0.445 inches to 0.465 inches;    -   a shell body adjoining said shoulder and having an interior        forming a main powder chamber for receiving an explosive charge;    -   a head adjoining said shell body and forming a base of said        shell case, said head having a primer pocket formed therein        communicating with said main powder chamber through a vent hole        formed between said primer pocket and said main powder chamber.

In accordance with an added feature of the invention, the shoulder isformed by a conical wall enclosing an angle of 20 to 45 degrees relativeto a longitudinal axis of the cartridge. This range of angles isparticularly suited for rimmed cartridges. In the context of a rimlesscartridge, the range is limited to 25 to 45 degrees.

In accordance with a preferred embodiment of the invention, the angle is30°, i.e., the shoulder walls enclose an angle of substantially 60° withone another. In the most preferred embodiment, the angle is 60° 00′28″.

In accordance with an added feature of the invention, the shoulder wallsmerge towards an imaginary apex lying on the longitudinal axis of thecartridge and the imaginary apex lies within the neck.

In accordance with a preferred embodiment of the invention, shell casehas a case length of 1.924 inches and the shoulder widens to a widestdiameter of 0.450 inches.

In accordance with a concomitant feature of the invention, the neck hasa diameter of substantially 0.315 inches to avoid confusion with 6.5 mmcaliber cartridges.

The invention described herein presents a new cartridge which is at alower energy potential but has similar or better features and ballisticsfor the preferred bullet weights at approximately 145 to 155 grain, ascompared with the prior art.

The novel cartridge uses a reduced case capacity compared with the 0.308Winchester cartridge. The heat from the burned powder charge is lower.This will result in a lower system and barrel warming result in a longeraction and barrel life.

Bullets with good aerodynamic features are defined by a long ovigneSpitzer bullet design in combination with a boat tail bullet form. Thiswill reduce air resistance and result in higher energy and bullet speedsand less bullet drop over longer shooting distances.

Bullet weights for shooting at longer distances or accuracy shooting aremostly above average bullet weights. Most in the upper half or third ofthe usable bullet weights are recommended for the caliber.

The cartridge chamber of the rifle must, of course, be formed tocorrespond with the cartridge dimensions and the bullets. Most similarcartridges have a short bullet overlap and transition to the groovedbarrel.

The shoulder angle to the mid axis influences barrel life and shootingprecision. A flat angle promotes burning powder fragments pushed intothe barrel from burning powder charge. A higher angle of approximately30 degrees to the mid-axis (double 60 degrees from shoulder to shoulder)supports burning of most powder fragments in the cartridge chamber. Muchhigher angles can cause misfire in repeating or self-loading rifles.

The novel cartridge is a good balanced cartridge with moderate recoil,controllable for rapid firing reduced action and barrel heating andstress. The novel cartridge has a relatively long bullet overlap whichis comparable with the popular good balanced 6.5 mm target bullets. Thisoverlap allows the use of a new good balanced aerodynamic styled targetbullet which previously did not exist at this bullet weight and caliber.

Although the cartridge starts at a reduced power level relative to the0.308 Winchester, it results in better data of speed energy and bulletdrop at the same mid-weighted bullet range. See Tables 1 to 3.

The preferred range of bullet weights from approximately 145 to 155grain is for the 6.8 caliber cartridge comparable with the higher bulletweights of the 0.308 cartridge and is a good choice for a long rangecartridge. The range of bullet weights is also above the popular 6.5 mmline.

The novel cartridge has a rim dimension to be adopted in actionschambered for the 0.308 Winchester. The body taper to 0.450″ diameter(P2) is improved for operation in bolt action and self loading weapons.

The novel cartridge can be easily integrated in existing systems andmagazine lengths adopted for the 0.308 Winchester.

As noted, the cartridge may be formed as a rimmed cartridge or as arimless cartridge. The rimmed cartridge is provided for break up gunsand combined guns. The remaining dimensions and data remain the same forthe rimmed and rimless versions, except that slightly alteredshoulder-powder room dimensions may be chosen. This applies, forinstance, to lower pressure versions for break up guns.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a rifle cartridge, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

The construction of the invention, however, together with additionalobjects and advantages thereof will be best understood from thefollowing description of the specific embodiment when read in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a longitudinal sectional view taken through a schematiccartridge casing according to the prior art;

FIG. 2 is a diagrammatic side view of a rimless cartridge according tothe invention shown with inch dimensions;

FIG. 3 shows the same cartridge in millimeter dimensions;

FIG. 4 illustrates a rimmed embodiment of the cartridge according to theinvention; and

FIG. 5 shows the same cartridge in millimeter dimensions.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is seen a longitudinal sectionthrough a cartridge provided in order to clarify the nomenclature usedherein. The illustrated cartridge is a rimless cartridge. Starting fromthe top, a bullet would be seated in a mouth 1 and a neck 2 would becrimped around the bullet in order to retain the same safely. Thecartridge then widens via a shoulder 3, which connects the neck 2 to abody 4. Here, the body 4 is completely cylindrical, without a chamferand therefore with a steady outer diameter from the shoulder/bodytransition to the bottom of the cartridge. As will be seen below, thenovel cartridge (0.270 Schuster) has a slight conicity as it widens fromthe shoulder down to the base.

The body 4 is adjoined by a head 5, which forms the base of thecartridge. The head 5 forms a belt 6 and a rim 7. Even though the figureillustrates a rimless cartridge, there is still provided a rim 7, whichis formed due to an extraction groove 8 formed between the belt 6 andthe rim 7. A primer pocket 9 is formed centrally in the base of the head5. The primer pocket 9 connects via a vent 10 into a main chamber 12. Inthis case, there is illustrated only a single vent hole, but it ispossible for two or more to be provided. The vent 10 is defined by aweb, which forms the wall between the primer pocket 9 and the chamber12.

Turning now to FIG. 2, there is shown an embodiment of the cartridgeaccording to the invention. The cartridge is shown with a Spitzer bulletand an overall length of 2.800″, or 71.12 mm. This corresponds to the0.308 Winchester and the standard 762 NATO round. The length of thecartridge shell is 1.924″ or 48.87 mm, which is considerably shorterthan the 0.308 Winchester (51.18 mm). The length of the neck is 0.300″,or 7.62 mm, again shorter than the 0.308 Winchester (7.70 mm).

The cartridge shell is also referred to as a shell case. The length ofthe shell case, measured from the mouth to the very bottom wall,according to the illustrated embodiments is 48.87″ or 1.924 mm. Theshell case length may be varied within a range of about 1.900″ to 1.950″and formed for standard .270 caliber bullets.

The shoulder 3 of the novel cartridge is quite pronounced, as theshoulder walls enclose an angle of slightly more than 60 degrees. Thecorresponding angle of the 0.308 Winchester is slightly more than 40degrees. That is, the imaginary apex of the shoulder 3 comes to lie justinside the neck 2 of the cartridge shell, at a distance of 1.8967″ or48.177 mm from the base. The corresponding apex of the 0.308 Winchestercomes to lie well ahead of the mouth 1, at a distance of 56.46 mm fromthe base.

The bullet illustrated here is a Spitzer bullet which, with properseating depth in the neck of the cartridge shell, results in an overalllength of the cartridge of 71.12 mm. It will be understood that any of aplurality of other bullet shapes are available as well. The primerpocket 9 is sized so as to accept and properly seat a “large rifle”primer.

The following the tables compare the novel cartridge with the 0.308Winchester cartridge loaded with the same bullet weights of 150 grainsas an example.

The muzzle speed of the novel cartridge is 2,657 feet per second (fps)and 2,710 fps for the 0.308 Winchester cartridge. Both cartridges are atthe same pressure level of 4.150 Bar (CIP).

These bullet speeds are calculated with “QuickLOAD Ballistic Program.”The speed data are an average formed from the 10 first listed loads fromthis calculation with different powders. The cartridges are loaded toapproximately 85% of maximal pressure level.

The data in the tables are given in steps of 25 yards from zero to 1,000yard distance. The data are calculated with SIERRA “Infinity ExteriorBallistics Software.”

150 grain Nosier bullets are used in these calculations as example. Thespread differences to 145 or 155 grain bullets are similar andproportional with light differences.

In a variation of the novel shell case, there is provided a strongerneck diameter (H1 and H2) at approximately 0.315″ (8 mm). This preventsthe cartridge from being loaded in smaller 6.5 mm caliber cartridges forsecurity reasons.

Tables 1A and 1B show wind drift at 5 and 10 miles per hour lightcrosswind, respectively. Higher wind drift is proportional to this data.The novel cartridge features result in a lower wind drift. The novelcartridge is identified as “0.270 SCH” while the reference cartridge isidentified as “0.308 WIN.”

TABLE 1A Range Wind Drift (Inches) (Yards) .270 SCH .308 WIN 25 0.020.03 50 0.09 0.11 75 0.21 0.25 100 0.37 0.44 125 0.59 0.7 150 0.86 1.01175 1.18 1.39 200 1.55 1.84 225 1.98 2.36 250 2.47 2.94 275 3.02 3.6 3003.63 4.34 325 4.3 5.15 350 5.04 6.05 375 5.84 7.03 400 6.72 8.09 4257.66 9.25 450 8.68 10.5 475 9.77 11.85 500 10.93 13.29 525 12.18 14.84550 13.51 16.5 575 14.92 18.26 600 16.41 20.14 625 18.0 22.13 650 19.6724.23 675 21.44 26.46 700 23.3 28.81 725 25.26 31.29 750 27.31 33.88 77529.46 36.61 800 31.72 39.46 825 34.08 42.44 850 36.54 45.54 875 39.148.76 900 41.78 52.1 925 44.55 55.55 950 47.43 59.12 975 50.42 62.791000 53.5 66.56

TABLE 1B Range Wind Drift (Inches) (Yards) .270 SCH .308 WIN 25 0.050.05 50 0.18 0.22 75 0.42 0.49 100 0.75 0.88 125 1.18 1.39 150 1.72 2.03175 2.36 2.79 200 3.11 3.68 225 3.97 4.71 250 4.95 5.89 275 6.04 7.21300 7.26 8.68 325 8.61 10.31 350 10.08 12.1 375 11.69 14.06 400 13.4316.19 425 15.32 18.5 450 17.35 21.0 475 19.53 23.7 500 21.87 26.59 52524.36 29.69 550 27.02 32.99 575 29.84 36.52 600 32.83 40.27 625 36.044.25 650 39.35 48.47 675 42.88 52.92 700 46.6 57.62 725 50.51 62.57 75054.62 67.77 775 58.93 73.22 800 63.44 78.92 825 68.16 84.87 850 73.0891.07 875 78.21 97.52 900 83.55 104.2 925 89.1 111.11 950 94.86 118.24975 100.83 125.58 1000 107.0 133.13

Table 2 shows the bullet drop. Although the novel cartridge starts at alower speed and energy level, the trajectory of the cartridge is flatterfor long range shooting. The bullet drop is better over approximately350 yard distance and below with little difference.

TABLE 2 Range Bullet Drop (Inches) (Yards) .270 SCH .308 WIN 25 0.160.15 50 0.63 0.61 75 1.44 1.39 100 2.59 2.51 125 4.09 3.98 150 5.97 5.82175 8.23 8.05 200 10.89 10.68 225 13.97 13.74 250 17.48 17.24 275 21.4321.21 300 25.86 25.67 325 30.77 30.64 350 36.19 36.15 375 42.14 42.23400 48.64 48.9 425 55.71 56.2 450 63.38 64.17 475 71.67 72.82 500 80.6282.21 525 90.24 92.37 550 100.57 103.35 575 111.65 115.17 600 123.49127.91 625 136.14 141.59 650 149.64 156.27 675 164.02 172.02 700 179.32188.87 725 195.58 206.9 750 212.84 226.16 775 231.16 246.71 800 250.57268.62 825 271.12 291.97 850 292.87 316.8 875 315.86 343.2 900 340.16371.22 925 365.8 400.95 950 392.85 432.43 975 421.36 465.75 1000 451.4500.95

Table 3 shows the bullet speed and energy. Although the novel cartridgestarts at a lower speed and energy level, the speed and energy aresuperior over approximately 125 yard distance and below with littledifference.

TABLE 3 .270 SCH .308 WIN Velocity Energy Range Velocity Energy (ft/sec)(ft/lbs) (Yards) (ft/sec) (ft/lbs) 2657.0 2350.9 0 2710.0 2445.7 2608.92266.6 25 2651.6 2341.4 2561.4 2184.8 50 2594.0 2240.7 2514.3 2105.2 752537.1 2143.6 2467.7 2027.9 100 2480.9 2049.6 2421.6 1952.8 125 2425.41958.9 2376.0 1879.9 150 2370.5 1871.3 2330.8 1809.2 175 2316.4 1786.92286.2 1740.5 200 2263.0 1705.4 2242.0 1673.9 225 2210.3 1626.9 2198.31609.2 250 2158.2 1551.1 2155.0 1546.5 275 2106.8 1478.9 2112.3 1485.8300 2056.2 1407.9 2070.0 1426.9 325 2006.3 1340.4 2028.2 1369.9 3501957.1 1275.5 1986.9 1314.7 375 1908.6 1213.1 1946.2 1261.3 400 1860.91153.2 1905.9 1209.7 425 1814.0 1095.8 1866.2 1159.8 450 1768.0 1040.91827.1 1111.7 475 1722.8 988.4 1788.5 1065.2 500 1678.5 938.2 1750.51020.4 525 1635.2 890.4 1713.1 977.3 550 1592.8 844.9 1676.4 935.9 5751551.5 801.6 1640.3 896.0 600 1511.2 760.5 1604.9 857.7 625 1472.1 721.71570.2 821.0 650 1434.2 684.9 1536.2 785.8 675 1397.4 650.3 1502.9 752.2700 1361.9 617.7 1470.5 720.1 725 1327.8 587.1 1438.9 689.4 750 1295.1558.6 1408.1 660.2 775 1263.9 532.0 1378.2 632.5 800 1234.2 507.3 1349.1606.1 825 1206.2 484.5 1321.1 581.2 850 1179.8 463.5 1294.0 557.6 8751155.1 444.3 1268.0 535.4 900 1132.0 426.8 1243.0 514.5 925 1110.6 410.81219.1 495.0 950 1090.8 396.2 1196.4 476.7 975 1072.5 383.1 1174.9 459.71000 1055.5 371.0

The term “substantially” as used in the claims is to be understood withreference to the respectively modified measurement or numerical value.The term varies and allows a modification of the associated value by amaximum of 3 to 6%. Where the modifier is not used in the context, theallowed variation is with the acceptable error range as understood bythose of skill in the art and will, typically, lie in the 1-2% range.

1. A rifle cartridge, comprising: a shell case having a case lengthbetween 1.900 inches and 1.950 inches and having a neck forming a mouthfor a standard .270 caliber bullet; a shoulder adjoining said neck andwidening from said neck to a diameter of between 0.445 inches to 0.465inches; a shell body adjoining said shoulder and having an interiorforming a main powder chamber for receiving an explosive charge; a headadjoining said shell body and forming a base of said shell case, saidhead having a primer pocket formed therein communicating with said mainpowder chamber through a vent hole formed between said primer pocket andsaid main powder chamber.
 2. The rifle cartridge according to claim 1,wherein said shoulder is formed by a conical wall enclosing an angle of20 to 45 degrees relative to a longitudinal axis of the cartridge. 3.The rifle cartridge according to claim 2, wherein said head is formedwith a rim rendering the cartridge a rimmed cartridge.
 4. The riflecartridge according to claim 2, wherein said conical wall encloses anangle of 25 to 45 degrees with the longitudinal axis of the cartridgeand the cartridge is formed as a rimless cartridge.
 5. The riflecartridge according to claim 1, wherein said shoulder walls enclose anangle of substantially 60° with one another.
 6. The rifle cartridgeaccording to claim 5, wherein said shoulder walls merge towards animaginary apex lying on the longitudinal axis of the cartridge and theimaginary apex lies within said neck.
 7. The rifle cartridge accordingto claim 1, wherein said shell case has a case length of 1.924 inches.8. The rifle cartridge according to claim 1, wherein said shoulderwidens to a widest diameter of 0.450 inches.
 9. The rifle cartridgeaccording to claim 1, wherein said neck has a diameter of substantially0.315 inches to avoid confusion with 6.5 mm caliber cartridges.